Prime number is a positive natural number that has only two positive natural number divisors - one and itself.
The opposite of prime numbers are composite numbers. A composite number is a positive nutural number that has at least one positive divisor other than one or itself.
The number 1 is not a prime number by definition - it has only one divisor.
The number 0 is not a prime number - it is not a positive number and has infinite number of divisors.
The number 15 has divisors of 1,3,5,15 because:
15/1=15
15/3=5
15/5=3
15/15=1
So 15 is not a prime number.
The number 13 has only two divisors of 1,13.
13/1=13
13/13=1
So 13 is a prime number.
List of prime numbers up to 100:
2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,...
The number 0 is not a prime number.
Zero is not a positive number and has infinite number of divisors.
The number 1 is not a prime number by definition.
One is has one divisor - itself.
The number 2 is a prime number.
Two has 2 natural number divisors - 1 and 2:
2 / 1 = 2
2 / 2 = 1